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Re: Canon EF 200400mm f/4L IS 1.4X: Quick Comparison  
I wonder why the number 1.4 is not taken seriously an approximation to the square root of 2.0, 1.414, so that stacking two of them produces a real 2.0x instead of 1.96x. Then a 400 x 1.4 x 1.4 should be 800 instead of 784. I'm arguably sure that this is the intent.
Or, in other words two stacked 1.4x's approximates one 2x.
Db
